Normal life should have resumed by now. But for many British workers, it seems, new year does not truly begin until well after Twelfth Night, with thousands now opting to extend their holidays beyond the usual Christmas period.

Yesterday, on the first official working day after the New Year break - apart from Scotland - streets and squares in London and other city centres typically thronged with commuters remained almost deserted, while the AA reported a very quiet day on the roads.

This year's longer winter break, or the great new year skive as it was bitterly being dubbed by some of those having to swap duvet for desk, reflects a growing trend for workers to take not only the entire Christmas and New Year period off, but to give a chunk of January a miss too, according to the Federation of Small Businesses.

It warned yesterday that UK workers' apparent reluctance to return to the grindstone could damage the economy. With many employees not back at work until next Monday, January 8, "the country will take some days to crank up again", according to spokesman Stephen Alambritis. "We have stiff competition from China and India and if we are all away until the 8th there is an impact."

While the trend for taking the time between Christmas and New Year as leave had become increasingly established over almost 10 years, the extension of holiday into January had emerged only in the last three years, he said.

Workers, he suggested, could be following the example of MPs, who do not return from the Christmas recess until Monday, or of celebrities hitting the ski slopes or beaches in warmer climes.

"We are not being curmudgeonly," said Mr Alambritis, who noted that workers were taking leave from their annual holiday entitlement. "We are just saying this is an increasing trend."

The FSB's assessment came as it emerged that some workers who were due to return to work yesterday appeared to have taken a tried and tested alternative option to booking leave: pulling a sickie. Official figures revealed that NHS Direct, the health helpline and website, was swamped by record levels of inquiries. Total traffic on its website was up by 30%, with 40,000 extra hits a day over Christmas, mainly concerning abdominal pain, dental problems and vomiting.

At the British Chambers of Commerce, director general David Frost said the quiet start to January was less a question of sickness than planned holiday. Working time regulations in force since 1998 had given workers four weeks' leave a year, which some were choosing to use at Christmas when they could combine them with bank holidays to create maximum time off for minimum holiday taken.

Employers were often content for workers to take time off at what was in any case a period of down time, he said.

At the Work Foundation, a thinktank which was itself running on a skeleton staff yesterday, researcher Stephen Overell said his own and similar organisations increasingly operated according to an "informal calendar" of extremely busy periods punctuated by quieter spells.

While thinktanks and others associated with policy worked frantically through the autumn, during party conferences and a busy period of the political cycle, they eased off at Christmas. Even when at work, there were some periods of "turbocharged" activity and others when staff were "at work theoretically but not psychologically present", he said.

In London yesterday, many organisations were operating but with more empty seats than usual. The Cabinet Office said its staff and those of other Whitehall departments had an allocation of leave and could request to take it when they chose, subject to agreement from bosses. "We try to stagger our leave during this period," said a spokeswoman. "We are open for business as usual."

Hammersmith hospital spokesman Nick Samuels said staff operated a system of "informal turn-taking", in which they would alternate time off and on at Christmas and other holidays from year to year.

The Construction Confederation said major building sites would not be operating until next week. "The official shutdown lasts until next Monday in line with the working rule agreement," said a spokesman. Jaguar, the car company, said its main Castle Bromwich factory near Birmingham had been closed for 10 days but a spokeswoman added: "We are all back in today."

Anyone there?

"Our office does seem rather quiet"CBI spokesman

"I walked [to work] through Parliament Square this morning and I seemed to be on my own ... We are definitely seeing January 8 as the key start to the year" Pret-a-Manger spokesman

"It's definitely quieter here. People with families want to spend time with their kids before the schools go back on Monday. I went to a restaurant at lunchtime and it was absolutely deserted"Goldman Sachs spokeswoman

"Shop floor workers were slaving away while the rest of us were enjoying our turkey" Spokesman for steel makers Corus

"It has always been said anecdotally that primary care shuts down over Christmas and New Year. GPs don't seem to be able to receive their Christmas presents from Santa Claus unless they are on the ski slopes" Anonymous hospital official, at work yesterday

"We expect the numbers of staff taking two weeks off this year to be roughly the same as last. We are pretty flexible about our holiday policy - we let people sell it back to the firm or buy extra days with a salary sacrifice" KPMG spokeswoman

"We are a 24-hour operation for large chunks of our business - we have to be. You can't shut down production on an oil well in the North Sea and leave it turned off for Christmas"BP spokesman